Why are ketones/aldehydes more oxidized than alcohols?

  • Thread starter hivesaeed4
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  • #1
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I thought that the reason was the presence of a double bond would allow oxygen to exert a stronger pull on the electrons making the co bond as compared to when their was only a double bind between the two but then I remembered that inductance happens only through sigma bonds So why are ketones/aldehydes more oxidized as compared to alcohols?
 

Answers and Replies

  • #2
Borek
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Many ways of skinning that cat.

First, and the simplest one - try to assign oxidation numbers to the carbon in methanol and methanal.

Can you write reaction equation of the R-CH2OH (a general primary alcohol) being converted to R-CHO (a general primary aldehyde)? What is removed from the alcohol molecule? How is the removed substance related to oxidation/reduction processes?
 
  • #3
Yep. Think in terms of oxidation state of the carbon atom.
 
  • #4
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Well you remove hydrogen and so that in itself is oxidation.

But I don't remember the oxidation states/numbers. I learned them in high school and don't exactly remember them. Why don't you tell me how to evaluate the oxidation state of the carbon atom. I tried understanding it from other online sources yet I didn't really understand it and am pretty sure that you guys would do a better job at it than websites do.
 
  • #5
chemisttree
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The more oxygen bonds a carbon has the more oxidized it is. An alcohol has one and ketones or aldehydes have two. Carbon dioxide has four and represents the most oxidized form of carbon in this series. A little different than memorizing the oxidation numbers of atoms you saw back in HS.
 
  • #6
Borek
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But I don't remember the oxidation states/numbers.
I tried understanding it from other online sources yet I didn't really understand it and am pretty sure that you guys would do a better job at it than websites do.
Really? I already prepared a website that explains these things, why do you think I will be better here than there:

(...)
Oxygen in almost all compounds has oxidation number -2.
Hydrogen in almost all compounds has oxidation number +1.
(...)
Last rule says that the charge of the ion or molecule equals sum of oxidation numbers of all atoms.
 
  • #7
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Thanks. By the way what was the name of the website your talking about Borek? I'd like to visit it. (I really didn't know you created one).
 
  • #9
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Thanks. Nice website.
 

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